P1175: THROMBOTIC RISK IN DLBCL: A REAL-LIFE COMPARISON OF THE THROLY AND MODEL IX SCORES
Authors: Ivan Civettini, Fabrizio Cavalca, Arianna Zappaterra, Stefano Crippa, Elena Agostani, Andrea Palasciano, Laura Antolinni, Federica Cocito, Carlo Gambacorti-Passerini
Journal: HemaSphere (2023)

Topic: 19. Aggressive Non-Hodgkin lymphoma - Clinical Background: Diffuse Large B Cell Lymphoma (DLBCL) patients (pts) carry a high risk of developing venous thromboembolism (VTE), with a 2-year cumulative incidence of 16%. The Throly and the recently published Model IX scores (Dharmavaram et al., 2020 AJH) can identify lymphoma pts at risk for thromboembolic event, but neither was developed specifically for DLBCL. Moreover the effectiveness of these two scores has never been compared in a real life DLBCL population. Aims: To evaluate the effectiveness of the Throly and Model IX scores on thrombotic risk in a real life DLBCL population, the incidence of VTE and the impact of thrombotic events on survival. Methods: Consecutive pts with a new diagnosis of DLBCL at the Lymphoma Unit of the IRCCS S.Gerardo Foundation, from January 2013 to November 2022, were enrolled. Patients with active anticoagulation therapy (therapeutic or prophylactic) were excluded. We analysed demographics, cardiovascular risk factors, thrombosis risk score (Throly and Model IX) and prognostic score for lymphoma (r-IPI). Results: A total of 208 pts were included: median age was 68 (range 27-92); 118 (57%) were male. 107 (51%) had a poor R-IPI score; 30 pts (14%) had at least a previous VTE event/ myocardial infarction/stroke. After a median follow up of 27 months (range 0,7-190), 32 VTE events (15.3%) were recorded: 9 (28%) lower extremities deep venous thrombosis (DVT), 7 pulmonary embolism (22%), 17 (53%) upper extremities or atypical DVT; 4 pts (12%) presented simultaneously with VTE in two different sites. Median time from lymphoma diagnosis to VTE was 22 days (range 0-439). According to Throly score 92 pts were low, 79 intermediate and 37 high risk, with a 2-year cumulative incidence of VTE of 8%, 20% and 24%, respectively. Having a high or intermediate (high-int) risk at diagnosis according to the Throly score was associated with a higher probability of developing VTE compared to low risk (p=0.0064). 91 pts (44%) were classified as high-int risk without developing VTE. According to Model IX score 56 pts were low and 152 high risk at diagnosis: we report a 2-year cumulative incidence of VTE of 2% and 20% respectively. High risk pts according to Model IX score had a higher probability of developing thrombosis compared to low-risk (p<0.001). 121 pts (58%) were classified as high risk without developing VTE. When comparing the Throly and Model IX score we didn’t find any significant difference (C-index=0.63vs0.63; AIC 8.3 lower for Model IX), unless the two scores were compared considering their single variables (C-index=0.66vs0.73; AIC 13 lower for Model IX). There was no difference in OS when comparing pts with and without VTE (p=0.83). Throly and Model IX high risk score was associated with shorter OS (p=0.04 and p=0.03). Summary/Conclusion: This retrospective study confirms that VTE is still a frequent complication for DLBCL pts, with a 2-year cumulative incidence of 15%. Throly and Model IX can predict VTE events in DLBCL pts with high sensitivity; pts with int-high and high risk respectively have a higher probability of developing VTE compared to those with low risk (p<0.01). Nevertheless, these scores tend to classify many patients as high risk and this impact negatively on specificity and on positive predictive value. A multivariable analysis comparison of the two risk models didn’t find any difference, unless they were compared considering their single variables; in this case Model IX seems to be the preferred model. Lastly, Throly and Model IX score can predict survival independently of VTE-mortality and IPI score.Keywords: Thrombosis, Diffuse large B cell lymphoma, Venous thrombosis, Lymphoma